Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $53.90   8.774%   $58.6292   $58.63   $58.65   $58.60  
  Purchase #2 $190.96   4.447%   $199.452   $199.45   $199.45   $199.50  
  Purchase #3 $18.61   6.115%   $19.748   $19.75   $19.75   $19.70  
  Purchase #4 $207.51   9.516%   $227.2567   $227.26   $227.25   $227.30  
  Purchase #5 $38.57   13.801%   $43.893   $43.89   $43.90   $43.90  
  Purchase #6 $11.66   6.758%   $12.448   $12.45   $12.45   $12.40  
  Purchase #7 $215.54   7.825%   $232.406   $232.41   $232.40   $232.40  
  7 purchase totals = $736.75       $793.8329   $793.84   $793.85   $793.80